OMV-mediated polymyxin B resistance in salmonella enterica SV. typhi : role of different genetic backgrounds and the presence of antibiotics
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Fecha
2022
Profesor/a Guía
Facultad/escuela
Idioma
en
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Universidad Andrés Bello
Nombre de Curso
Licencia CC
Licencia CC
Resumen
Cepas multirresistentes han dado paso a la reintroducción de antibióticos de
última línea, como las polimixinas que ejercen su acción en la envoltura. El
principal mecanismo de resistencia a polimixina B está relacionado a cambios en
la envoltura, sin embargo, otros mecanismos siguen siendo reportados. Las
vesículas de membrana externa (OMVs) son proteoliposomas derivados de la
membrana externa de bacterias gram negativo que pueden variar en
características y funciones. Una función de interés es la resistencia frente a
antibióticos. Se ha reportado que OMVs son capaces de capturar o expulsar
moléculas de la bacteria, bajando su concentración efectiva. Estudios recientes
relacionados a Salmonella Typhi muestran que ciertas mutaciones afectan la
biogénesis de OMVs, como ΔrfaE (LPS), ΔtolR (envoltura) y ΔdegS (proteínas
mal plegadas). Hay reportes de bacterias donde la polimixina B incrementa la
producción de OMVs. En S. Typhi ciertos estímulos ambientales pueden modular
la biogénesis de OMVs. Sin embargo, el impacto de OMVs en mutantes de S.
Typhi o la cepa silvestre (WT) bajo estímulos ambientales no ha sido estudiado
en la resistencia contra polimixina B. En este estudio exploramos el impacto de
deleciones genéticas relacionadas a la biogénesis de OMVs y la presencia de
antibióticos en la resistencia frente a polimixina B. Encontramos que OMVs
derivadas de las mutantes ΔtolR y ΔdegS protegen a S. Typhi de una manera
dependiente de la concentración. Esto debido al secuestro de polimixina B
observado en los cambios de potencial Zeta y su menor disponibilidad luego del
tratamiento. Por otro lado, OMVs de ΔrfaE no tuvieron diferencias significativas
comparadas con la WT. Se evaluó la posibilidad de transferencia de protección
frente a polimixina B en co-cultivos donde las cepas ΔtolR y en menor medida
ΔdegS pudieron proteger a bacterias sensibles a polimixina B. Finalmente, se
evaluó el efecto de un tratamiento subletal de ampicilina sobre la biogénesis de
OMVS. Encontramos un aumento significativo en el tiempo de duplicación y la
mínima concentración inhibitoria (MIC) contra polimixina B cuando S. Typhi es
tratada previamente con ampicilina. Este efecto fue atribuido al incremento de
biogénesis de OMVs generado por el tratamiento previo con ampicilina
Multi-resistant strains have led to the reintroduction of last line antibiotics such as polymyxins. They exert their effect in the bacterial envelope leading to cell death. The main mechanism of polymyxin resistance is related to changes to the bacterial envelope, although other resistance mechanisms have been reported. Outer membrane vesicles (OMVs) are proteoliposomes derived from the outer membrane of Gram-Negative bacteria. These OMVs vary in different characteristics and functions, one of them acting as an antibiotic resistance mechanism. OMVs have been reported to capture or expel dangerous molecules from the bacteria, thus lowering their effective concentration. Recent studies regarding Salmonella Typhi show that certain mutations affect OMV biogenesis, such as ΔrfaE (LPS synthesis), ΔtolR (bacterial envelope) and ΔdegS (misfolded proteins). There have been reports on gram-negative bacteria where polymyxin B increases OMV production. On S. Typhi, it has been reported that certain environmental stimuli can modulate OMV biogenesis. Although, the impact of OMVs from S. Typhi mutants and the WT under environmental stimuli has not been addressed in polymyxin B resistance. In this study we explored the impact of gene deletions related to OMV biogenesis and the presence of antibiotics in polymyxin B resistance. We found that OMVs derived from the mutants ΔtolR and ΔdegS protect S. Typhi in a concentration dependent manner against polymyxin B. This is due to the sequestration of polymyxin B as seen by the changes in the Zeta potential and the lower availability after treatment. In contrast, OMVs from ΔrfaE had no significant differences with the low protective effect from the WT. The potential of polymyxin B resistance transferring was tested in cocultures were ΔtolR and to a lesser extend ΔdegS, were able to protect polymyxin B susceptible bacteria. Finally, we tested the effect of a sublethal treatment of ampicillin in OMVmediated polymyxin B resistance. We found that there is a significant increase in duplication time and minimum inhibitory concentration (MIC) against polymyxin B when S. Typhi is previously treated with ampicillin. This effect was attributed to the increase in OMV biogenesis due to the ampicillin treatment.
Multi-resistant strains have led to the reintroduction of last line antibiotics such as polymyxins. They exert their effect in the bacterial envelope leading to cell death. The main mechanism of polymyxin resistance is related to changes to the bacterial envelope, although other resistance mechanisms have been reported. Outer membrane vesicles (OMVs) are proteoliposomes derived from the outer membrane of Gram-Negative bacteria. These OMVs vary in different characteristics and functions, one of them acting as an antibiotic resistance mechanism. OMVs have been reported to capture or expel dangerous molecules from the bacteria, thus lowering their effective concentration. Recent studies regarding Salmonella Typhi show that certain mutations affect OMV biogenesis, such as ΔrfaE (LPS synthesis), ΔtolR (bacterial envelope) and ΔdegS (misfolded proteins). There have been reports on gram-negative bacteria where polymyxin B increases OMV production. On S. Typhi, it has been reported that certain environmental stimuli can modulate OMV biogenesis. Although, the impact of OMVs from S. Typhi mutants and the WT under environmental stimuli has not been addressed in polymyxin B resistance. In this study we explored the impact of gene deletions related to OMV biogenesis and the presence of antibiotics in polymyxin B resistance. We found that OMVs derived from the mutants ΔtolR and ΔdegS protect S. Typhi in a concentration dependent manner against polymyxin B. This is due to the sequestration of polymyxin B as seen by the changes in the Zeta potential and the lower availability after treatment. In contrast, OMVs from ΔrfaE had no significant differences with the low protective effect from the WT. The potential of polymyxin B resistance transferring was tested in cocultures were ΔtolR and to a lesser extend ΔdegS, were able to protect polymyxin B susceptible bacteria. Finally, we tested the effect of a sublethal treatment of ampicillin in OMVmediated polymyxin B resistance. We found that there is a significant increase in duplication time and minimum inhibitory concentration (MIC) against polymyxin B when S. Typhi is previously treated with ampicillin. This effect was attributed to the increase in OMV biogenesis due to the ampicillin treatment.
Notas
Tesis (Licenciado en Biología)
Palabras clave
Salmonella Typhi, Resistencia Microbiana a las Drogas, Polimixina